Implementing coherent accelerator function isolation for virtualization

ABSTRACT

A method, system and computer program product are provided for implementing coherent accelerator function isolation for virtualization in an input/output (IO) adapter in a computer system. A coherent accelerator provides accelerator function units (AFUs), each AFU is adapted to operate independently of the other AFUs to perform a computing task that can be implemented within application software on a processor. The AFU has access to system memory bound to the application software and is adapted to make copies of that memory within AFU memory-cache in the AFU. As part of this memory coherency domain, each of the AFU memory-cache and processor memory-cache is adapted to be aware of changes to data commonly in either cache as well as data changed in memory of which the respective cache contains a copy.

FIELD OF THE INVENTION

The present invention relates generally to the data processing field,and more particularly, relates to a method, system and computer programproduct for implementing coherent accelerator function isolation forvirtualization in an input/output (IO) adapter in a computer system.

DESCRIPTION OF THE RELATED ART

Coherent accelerators may be utilized within the scope of a singleoperating system image, whether that operating system (OS) is one of aplurality on a logically partitioned server, or the sole operatingsystem of a non-partitioned system. However, it is desirable to enable acoherent accelerator to be shared, or virtualized, across a plurality ofoperating system images on a logically partitioned system. A fundamentalrequirement to enable sharing is that Peripheral Component InterconnectExpress (PCIE or PCI-Express) transactions, including for example,direct memory accesses (DMAs), message signaled interrupts,memory-mapped Input/Output (IO), and error events, be isolated betweenOS images and accelerator functions.

PCI-Express (PCIE) enables virtualizing sub-functions of a PCIE deviceusing Single Root IO Virtualization (SRIOV). Single root input/output(IO) virtualization (SRIOV) is a PCI standard, providing an adaptertechnology building block for I/O virtualization within the PCI-Express(PCIe) industry. The SRIOV architecture encapsulates resources within aPCI-Express IO adapter behind a Virtual Function (VF) that in manyrespects operates as a conventional PCI-Express device. Isolation of VFsfrom each other and operating system images other than those to whichthe VFs are individually assigned is accomplished by use of translationtables, such as Hardware Page Tables that translate processorinstruction addresses to PCI-Express memory addresses or memory-mappedI/O (MMIO) and DMA translation tables that translate PCI-Express devicememory read/write addresses to system memory addresses.

Utilizing either conventional PCI or SRIOV devices, MMIO and DMA domainsare associated with a PCI function having a bus/device/function(requester ID, or RID) association. Additionally, DMA translation mayinclude Message Signaled Interrupt (MSI), (DMA write) isolation, by anOS or hypervisor authorizing a particular set of MSI vectors toparticular MSI or DMA addresses. For example, IBM POWER systems IODevice Architecture, (IODA) for PCI-Express, as well as Intel VT-Darchitecture, exemplify these techniques.

IBM POWER systems IODA provides a means to associate MMIO, DMA, and MSIaddresses with a RID to facilitate isolating errors involving MMIO, DMA,or MSI transactions on the PCI-Express bus to a particular PCI-Expressfunction, utilizing the RID and tables within POWER PCI-Express rootcomplexes or PCI-Express host bridges (PHBs). Within the art it isunderstood that a PCI host bridge (PHB) is an element within a PCI rootcomplex, and may in a particular design be in whole an instance of aroot complex.

However, aspects of SRIOV complicate the design of a coherentaccelerator function, or may not be compatible with the acceleratoroperation. For example, units within a processor communicate with anaccelerator to synchronize the state of memory cache lines that may beheld in common in the accelerator itself. While this communication mayuse PCI-Express memory read/write transactions, to communicate cacheline updates, or to retrieve changed cache lines from an accelerator,the references to cache lines using PCI-Express memory read/writetransactions may be structured in terms of system memory, and have noability to relate these directly to SRIOV type virtual functions. (VFs).

A need exists for an effective method and apparatus to achieve coherentaccelerator function isolation for virtualization, such as to achieveisolation of MMIO, DMA, MSI, and errors at a PCI-Express transactionlevel, without requiring the use of other PCI-Express virtualizationmechanisms, such as SRIOV. A need exists to reduce complexity in thedesign of the processor and accelerator to enable use of simplePCI-Express memory read/write transactions by either of them, withoutintroducing additional and unnecessary concepts of SRIOV.

SUMMARY OF THE INVENTION

Principal aspects of the present invention are to provide a method,system and computer program product for implementing coherentaccelerator function isolation for virtualization. Other importantaspects of the present invention are to provide such method, system andcomputer program product substantially without negative effects and thatovercome many of the disadvantages of prior art arrangements.

In brief, a method, system and computer program product are provided forimplementing coherent accelerator function isolation for virtualizationin an input/output (IO) adapter in a computer system. A coherentaccelerator provides accelerator function units (AFUs), each AFU isadapted to operate independent of the other AFUs to perform a computingtask that can be implemented within application software on a processor.The AFU has access to system memory bound to the application softwareand is adapted to make copies of that memory within AFU memory-cache inthe AFU. As part of this memory coherency domain, each of the AFUmemory-cache and processor memory-cache is adapted to be aware ofchanges to data commonly in either AFU memory-cache or processormemory-cache as well as data changed in memory of which the respectivecache contains a copy.

In accordance with features of the invention, to maintainsynchronization between the AFU memory-cache and the processormemory-cache, the processor and accelerator communicate changes toindividual memory regions, for example represented as cache lines.

In accordance with features of the invention, use of simple PCI-Expressmemory read/write transactions by the processor and the accelerator isenabled when using a PCI-Express interconnect, with design complexity ofthe processor and the accelerator advantageously reduced, withoutrequiring additional and unnecessary concepts of SRIOV. A coherentaccelerator utilizes a PCI Services Layer (PSL) endpoint function withinthe adapter to effect PCI transactions associated with the AFUs

In accordance with features of the invention, a hypervisor adapterdriver in support of a PCI-Express interface associates each AFU withPCI host bridge (PHB) isolation facilities.

In accordance with features of the invention, when using PCI-Expressinterconnect between each AFU and a processor and memory, the processorand AFU utilize PCI-Express memory read/write operations. An AFU isassociated with a PCI-Express requester ID (RID) for identifying thatAFU during the PCI-Express memory read/write operations effecting AFUDMA to or from system memory. An AFU is associated with a RID forpurposes of a PHB associating processor MMIO addresses with an AFU.

In accordance with features of the invention, requests to perform a taskand result of completing that task are exchanged between an applicationrunning within an operating system (OS) and the AFU usingcommand/response queues within system memory, the AFU, or a combinationof both. The individual AFUs either respond to or originate PCI-Expressmemory cycles, and the accelerator adapter PSL performs the PCI-Expresstransactions corresponding to those memory read/write operations.

In accordance with features of the invention, the AFUs are recognizedand operated by an operating system (OS) as particular types ofmemory-mapped AFU devices and optionally in a manner in which they arecompletely unassociated with PCI-Express buses or functions, within theoperating system.

In accordance with features of the invention, a PCI-Express PHBoptionally is used to associate Memory-mapped IO (MMIO), Direct MemoryAccess (DMA), Message Signaled Interrupt (MSI) address ranges withPCI-Express RIDs (Relative Identifiers) to associate these addressranges with individual accelerator function unit (AFU) that are nototherwise configured and operate on the PCI-Express bus as endpointfunctions.

In accordance with features of the invention, a hypervisor or othersystem configuration and management software or firmware in support ofPCI-Express buses and managing the coherent accelerator as a wholedetects and recovers error involving the PSL or AFUs, without requiringthe termination of any one OS to restore operation of its respectiveAFU, with the AFUs sharing a common PSL endpoint function on thePCI-Express bus.

In accordance with features of the invention, a hypervisor or othersystem configuration and management software or firmware in support ofPCI-Express buses associates AFUs with PHB isolation facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above and other objects andadvantages may best be understood from the following detaileddescription of the preferred embodiments of the invention illustrated inthe drawings, wherein:

FIG. 1 illustrates an example system for implementing coherentaccelerator function isolation for virtualization in an input/output(IO) adapter with a single BDF (bus/device/function) in accordance witha preferred embodiment;

FIG. 2 illustrates another example system for implementing enhancedcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter with multiple BDFs in accordance with apreferred embodiment;

FIG. 3 illustrates example operational features for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter of FIG. 1 and FIG. 2 with comparison ofexisting art in accordance with preferred embodiments;

FIG. 4 illustrates example operational features for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter of FIG. 1 in accordance with preferredembodiments;

FIG. 5 illustrates example operational features for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter of FIG. 2 in accordance with preferredembodiments;

FIGS. 6, 7, and 8 are flow charts illustrating example system operationsof the systems of FIGS. 1 and 2 for implementing coherent acceleratorfunction isolation in accordance with preferred embodiments; and

FIG. 9 is a block diagram illustrating a computer program product inaccordance with the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of embodiments of the invention,reference is made to the accompanying drawings, which illustrate exampleembodiments by which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In accordance with features of the invention, a method, system andcomputer program product are provided for implementing coherentaccelerator function isolation for virtualization in an input/output(IO) adapter.

Having reference now to the drawings, in FIG. 1, there is shown anexample computer system generally designated by the reference character100 for implementing coherent accelerator function isolation forvirtualization in an input/output (IO) adapter in accordance with thepreferred embodiment. Computer system 100 includes one or moreprocessors, such as processor #1, 102 through processor #N, 104 orcentral processor units (CPUs) 102, 104 coupled by a system bus 106 to amemory 108, a respective host operating system (OS) 110, 112, and ahypervisor adapter driver 114. The hypervisor adapter driver 114 is apart of the system firmware and manages the allocation of resources toeach operating system 110, 112.

Computer system 100 can be utilized within the scope of a singleoperating system image, whether that operating system (OS) is one of aplurality on a logically partitioned server, or the sole operatingsystem of a non-partitioned system. Computer system 100 enables acoherent accelerator to be shared, or virtualized, across a plurality ofoperating system (OS) images on a logically partitioned system.

Computer system 100 includes an I/O hub, processor host bridge or PCIEhost bridge (PHB) 120 providing coherent accelerator PE (PartitionableEndpoint) support in accordance with the preferred embodiment. PHB 120includes an adapter PE 122 coupled to the hypervisor adapter driver 114,and an AFU PE 124 coupled to each respective host operating system (OS)110, 112. PHB 120 includes isolation facilities 126 provided with AFU PE124.

Computer system 100 includes an Input/Output (I/O) adapter 130 providinga coherent accelerator with transaction layer functions including forexample, a PCI Services Layer (PSL) 132, and a plurality of AFUs 1-3,134, 136, 138, with the PSL 132, and each AFUs 1-3, 134, 136, 138coupled to the adapter PE 122. AFUs 1-3, 134, 136, 138 are logic unitswithin the accelerator that perform specific application tasks.

In accordance with features of the invention, isolation facilities 126within the PCI-Express PHB 120 are used particularly including errorisolation without requiring the use of a PCI-Express endpoint function.Methods of the invention detect and recover from PCI-Express errorconditions involving individual AFUs, the AFUs as a collective, and thePSL. The operating system and application are enabled to continue tofunction through interacting with the error recovery methods, so that areboot of the operating system is not required, and so that individualoperating systems may individually recover operation of their respectiveAFUs even though the accelerator device is shared at a singlePCI-Express endpoint function.

In a particular embodiment requests to perform a task and result ofcompleting that task are exchanged between the application runningwithin OS 110, or OS 112 and the respective AFUs 1-3, 134, 136, 138using command/response queues within system memory 108, the AFU, or acombination of both. Each of the individual AFUs 1-3, 134, 136, 138either respond to or originate PCI-Express memory cycles, and the PSL132 performs the PCI-Express transactions corresponding to those memoryread/write operations. However, the AFUs 1-3, 134, 136, 138 are notthemselves PCI-Express endpoint devices or functions and may not berecognized by an operating system as PCI-Express devices. Instead, theAFUs are recognized and operated by OS 110, or OS 112 as particulartypes of memory-mapped AFU devices and possibly in a manner in whichthey are completely unassociated with PCI-Express buses or functions,within the respective operating system.

Computer system 100 enables coherent accelerator adapter functionalitywith the additional AFU PE 124 that is associated with all AFUs 1-3,134, 136, 138, collectively. Host OS MMIO activities are governed by theAFU PE 124. The AFU PE 124 can be frozen such that the host OSs 110, 112are blocked from accessing the adapter 130. The AFU PE 124 allows thehypervisor 114 to complete recovery or maintenance actions without thepossibility of a host OS user impacting the adapter 130. Transactions ofadapter 130, both those associated with the PSL 132 as well thoseassociated with the AFUs-3, 134, 136, 138, utilize the adapter PE 122.Any failure from the adapter PE 122 still impacts all OS partitionsusing the coherent accelerator adapter 130.

Computer system 100 is shown in simplified form sufficient forunderstanding the present invention. The illustrated computer system 100is not intended to imply architectural or functional limitations. Thepresent invention can be used with various hardware implementations andsystems and various other internal hardware devices.

Referring to FIG. 2, there is shown another example system generallydesignated by the reference character 200 for implementing coherentaccelerator function isolation for virtualization in an input/output(IO) adapter 230 with multiple BDFs in accordance with a preferredembodiment. Computer system 200 similarly includes one or moreprocessors, such as processor #1, 102 through processor #N, 104 orcentral processor units (CPUs) 102, 104 coupled by a system bus 106 to amemory 108, a respective host operating system (OS) 110, 112, and ahypervisor adapter driver 114.

Computer system 200 includes an I/O hub, processor host bridge or PCIEhost bridge (PHB) 220 providing coherent accelerator PE (PartitionableEndpoint) support in accordance with the preferred embodiment. PHB 220includes an adapter PE 222 coupled to the hypervisor adapter driver 114,and a plurality of AFU PE 1-3, 224, 226, 228 with AFU PE 1-2, 224, 226coupled to host OS 110 and AFU PE 3, 228 coupled to host OS 112, asshown. PHB 220 includes isolation facilities 226 provided with AFU PE1-3, 224, 226, 228.

Computer system 200 includes an Input/Output (I/O) adapter 230 providinga coherent accelerator with transaction layer functions including forexample, a PCI Services Layer (PSL) 232 providing all functions andfacilities consistent with a PCIE endpoint function, and a plurality ofAFUs 1-3, 234, 236, 238, with the PSL 232 coupled to the adapter PE 222,and each AFUs 1-3, 234, 236, 238 coupled to a respective AFU PE 1-3,224, 226, 228.

Computer system 200 enables coherent accelerator adapter enhancedfunctionality with the additional AFU PEs 1-3, 224, 226, 228, eachassociated with the respective AFUs 1-3, 234, 236, 238. When the adapter230 does DMA transactions it encodes the respective one of AFUs 1-3,234, 236, 238 performing the transaction, for example, using AlternativeRouting-ID Interpretation (ARI) techniques into the DMA packets. Thisallows for fault isolation down to a single one of AFUs 1-3, 234, 236,238 while still only implementing a single PCI function with a singleconfiguration space. This is an increasingly important and valuablefeature as the number of AFUs on an adapter 230 increases.

Host OS MMIO activities are governed by the respective AFU PEs 1-3, 224,226, 228. Each respective AFU PEs 1-3, 224, 226, 228 advantageously canbe frozen such that the host OSs 110, 112 are blocked from accessing theadapter 230. Each of the respective AFU PEs 1-3, 224, 226, 228 allowsthe hypervisor 114 to complete recovery or maintenance actions withoutthe possibility of a host OS user impacting the adapter 230.Transactions associated with the PSL 232 of adapter 230 utilize theadapter PE 222. Any failure from the adapter PE 222 still impacts all OSpartitions using the coherent accelerator adapter 230.

In accordance with features of the invention, PCI-Express PHB 120apparatus is used to associate Memory-mapped IO (MMIO), Direct MemoryAccess (DMA), Message Signaled Interrupt (MSI) address ranges withPCI-Express RIDs (Relative Identifier) to associate these address rangeswith each of the individual Accelerator function units AFUs 1-3, 234,236, 238 that are not otherwise configured and operate on thePCI-Express bus as endpoint functions.

In accordance with features of the invention, the hypervisor adapterdriver 114 in support of a PCI-Express interface associates each of theAFUs 1-3, 234, 236, 238 with PHB isolation facilities 226. Thehypervisor adapter driver 114, managing the coherent accelerator as awhole, detects and recovers error involving the PSL 232 or AFUs 1-3,234, 236, 238, without requiring the termination of any one OS 110, 112to restore operation of its respective AFU, with the AFUs sharing acommon PCI Services Layer (PSL) endpoint function on the PCI-Expressbus. The hypervisor adapter driver 114 in support of PCI-Express busesassociates AFUs with PHB isolation facilities 226.

In accordance with features of the invention, the PSL 232 of a coherentaccelerator RID is associated with the MMIO, DMA, MSI, and error statefacilities 226 of a PCI-Express PHB 220, and the PCI-Express RID isassociated with a collective of AFUs AFUs 1-3, 234, 236, 238 and furtherassociating AFUs 1-3, 234, 236, 238 residing behind the respective PSL232 with the PCI-Express PHB 220 without the AFU RID being itself anindividual PCI-Express endpoint or SRIOV virtual functions and havingall the facilities and behaviors of such functions.

In accordance with features of the invention, when using PCI-Expressinterconnect between each AFU of AFUs 1-3, 234, 236, 238 and processor102, 104 and memory 108, the processor and AFU utilize PCI-Expressmemory read/write operations. An AFU of AFUs 1-3, 234, 236, 238 isassociated with a PCI-Express requester ID (RID) for identifying thatAFU during the PCI-Express memory read/write operations.

Referring to FIG. 3, there are shown example operational featuresgenerally designated by the reference character 300 for implementingcoherent accelerator function isolation for virtualization in theinput/output (IO) adapter 130 in system 100 of FIG. 1 and input/output(IO) adapter 230 in system 200 of FIG. 2 with comparison of existing artin accordance with preferred embodiments, without relying uponfacilities or operations of PCIE SRIOV.

Multiple features 302 are shown for comparison of known existing art,with IO adapter 130 in system 100 of FIGS. 1 and IO adapter 230 insystem 200 of FIG. 2. One endpoint function 304 is included in the knownexisting art, IO adapter 130 in system 100 and IO adapter 230 in system200. A single configuration space region 306 is included in the knownexisting art, IO adapter 130 in system 100 and IO adapter 230 in system200. An additional PCIE RID 308 is included in the IO adapter 230 insystem 200, with zero included in the known existing art, and in the IOadapter 130 in system 100. A single adapter PE 310 is included in theknown existing art, IO adapter 130 in system 100 and IO adapter 230 insystem 200. One AFU PE 312 is included in the IO adapter 130 in system100 and one AFU PE 312 per AFU is included in the IO adapter 230 insystem 200, with zero AFU PE 312 included in the known existing art.Error recovery 314 is not possible in the known existing art with thehost OS reboot required. Error recovery 314 is possible in the IOadapter 130 in system 100 with all host OS instances impacted. Improvederror recovery 314 is possible in the IO adapter 230 in system 200 witha finer grain and a single host OS instances impacted.

Referring to FIG. 4, there are shown example operational featuresgenerally designated by the reference character 400 for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter 130 in system 100 of FIG. 1 in accordance withpreferred embodiments without relying upon facilities or operations ofPCIE SRIOV. Multiple traffic types 402 are shown with a respective PEused 404, error action 406, and error impact 408. With traffic type 402of MMIO initiated by the hypervisor adapter driver, the PE used 404 isthe adapter PE, error action 406 causes the PHB isolation facilities 126to freeze adapter PE plus AFU PE, and the error impact 408 includes thehypervisor adapter driver and all host OS instances. With traffic type402 of MMIO initiated by the host OS to a particular AFU n, the PE used404 is the AFU PE, error action 406 causes the PHB isolation facilities126 to freeze the AFU PEs, and the error impact 408 includes all host OSinstances. With traffic type 402 of DMA initiated by adapter PSL, the PEused 404 is the adapter PE, error action 406 causes the PHB isolationfacilities 126 to freeze the adapter PE and the AFU PE, and the errorimpact 408 includes the hypervisor adapter driver and all host OSinstances. With traffic type 402 of DMA initiated by a particular AFU n,the PE used 404 is the adapter PE, error 406 freezes the adapter PE andthe AFU PE, and the error impact 408 includes the hypervisor adapterdriver and all host OS instances.

Referring to FIG. 5, there are shown example operational featuresgenerally designated by the reference character 500 for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter 230 in system 200 of FIG. 2 in accordance withpreferred embodiments. Multiple traffic types 502 are shown with arespective PE used 504, error action 506, and error impact 508. Withtraffic type 502 of MMIO initiated by the hypervisor adapter driver, thePE used 504 is the adapter PE, error action 506 causes the PHB isolationfacilities 226 to freeze adapter PE plus AFU PEs, and the error impact508 includes the hypervisor adapter driver and all host OS instances.With traffic type 502 of MMIO initiated by the host OS to a particularAFU n, the PE used 504 is the particular AFU PE n, error action 506causes the PHB isolation facilities 226 to freeze the AFU PE n, and theerror impact 508 includes the single host OS instances. With traffictype 502 of DMA initiated by adapter PSL, the PE used 504 is the adapterPE, error action 506 causes the PHB isolation facilities 226 to freezethe adapter PE and the AFU PEs, and the error impact 508 includes thehypervisor adapter driver and all host OS instances. With traffic type502 of DMA initiated by a particular AFU n, the PE used 504 is the AFUPE n, error action 506 causes the PHB isolation facilities 226 to freezethe AFU PE n, and the error impact 508 includes a single host OSinstances.

FIGS. 6, 7, and 8 are flow charts illustrating example system operationsof the systems of FIGS. 1 and 2 for implementing coherent acceleratorfunction isolation in accordance with preferred embodiments.

Referring to FIG. 6, there are shown example high level systemoperations of the systems of FIGS. 1 and 2 starting with PHB or rootcomplex hardware or hypervisor adapter driver detects failure andfreezes the adapter PE as indicated in a block 600. As indicated in ablock 602, other PEs associated with the adapter PE are frozen includingall AFU PEs. In the event that the PHB hardware detects the failure thehardware informs hypervisor of the frozen PEs as indicated in a block604. The hypervisor informs PE owners of the frozen PEs including bothadapter driver and host OS for each AFU as indicated in a block 606. Theadapter driver and each host OS asynchronously begin recovery asindicated in a block 608.

Referring also to FIG. 7, there are shown example hypervisor driveroperations of the systems of FIGS. 1 and 2 starting when the adapterdriver receives notification of error as indicated in a block 700. Theadapter driver commences PE recovery as indicated in a block 702. Theadapter driver unfreezes the adapter PE with other PEs remaining frozen,collects error data, and commences recover as indicated in a block 704.The adapter driver recovers the adapter and restores the adapter to adefault state as indicated in a block 706. The adapter driver performsAFU configuration to the adapter as indicated in a block 708. Theadapter driver logs error and communicates a PCI error log identifier(PLID) for the error logged by the adapter driver to the hypervisor asindicated in a block 710. The adapter drives gives the hypervisorpermission to unfreeze AFU PE(s) and resumes normal operation asindicated in a block 712.

Referring to FIG. 8, there are shown example host OS operations of thesystems of FIGS. 1 and 2 starting with host OS receives notification ofAFU error as indicated in a block 800. The host OS commences recovery asindicated in a block 802. The host OS loops attempting to unfreeze AFUPE, and the unfreeze is unsuccessful until the adapter driver completesrecovery as indicated in a block 804. As indicated in a block 806, theadapter driver completes recovery. Then the host OS unfreezes the AFUPE, retrieves error data and commences recovery as indicated in a block808. The host OS completes recovery, and logs error data as indicated ina block 810. Normal AFU operations resume as indicated in a block 812.

Referring now to FIG. 9, an article of manufacture or a computer programproduct 900 of the invention is illustrated. The computer programproduct 900 is tangibly embodied on a non-transitory computer readablestorage medium that includes a recording medium 902, such as, a floppydisk, a high capacity read only memory in the form of an optically readcompact disk or CD-ROM, a tape, or another similar computer programproduct. Recording medium 902 stores program means 904, 906, 908, and910 on the medium 902 for carrying out the methods for implementingcoherent accelerator function isolation for virtualization in aninput/output (IO) adapter 130, 230 of preferred embodiments in thesystem 100 of FIG. 1, or system 200 of FIG. 2.

A sequence of program instructions or a logical assembly of one or moreinterrelated modules defined by the recorded program means 909, 906,908, and 910, direct the computer system 900 for implementing coherentaccelerator function isolation for virtualization in an input/output(IO) adapter 130, 230 of preferred embodiments.

While the present invention has been described with reference to thedetails of the embodiments of the invention shown in the drawing, thesedetails are not intended to limit the scope of the invention as claimedin the appended claims.

What is claimed is:
 1. A system for implementing coherent acceleratorfunction isolation for virtualization in an input/output (IO) adaptercomprising: a processor; a hypervisor managing functions associated withthe hardware I/O adapter; the I/O adapter comprising a coherentaccelerator including an interface services layer providingPartitionable Endpoint (PE) functions and multiple accelerator functionunits (AFUs); each AFU being enabled to operate independently of theother AFUs to perform a computing task that can be implemented withinapplication software on a processor; each AFU having access to systemmemory bound to the application software and each AFU being adapted tomake copies of memory within AFU memory-cache in the AFU; and each ofthe AFU memory-cache and processor memory-cache being adapted to beaware of changes to data commonly in either cache as well as datachanged in memory of which the respective cache contains a copy formemory coherency domain.
 2. The system of claim 1, further comprising aPeripheral Component Interconnect Express (PCIE) host bridge (PHB)providing coherent accelerator PE (Partitionable Endpoint) supportincluding an adapter PE and an AFU PE; wherein said AFUs are recognizedand operated by an operating system (OS) as memory-mapped AFU devices;and wherein said hypervisor detects and recovers error involving theinterface services layer or AFUs, without requiring the termination ofthe operating system (OS) to restore operation of its respective AFU,with the AFUs sharing a common PCI-Express Services Layer (PSL) endpointfunction.